Deep sea mining system

ABSTRACT

A deep sea mining system for mining ore from the surface of an ocean bed using a mining plant that travels the bed, a Sessile ship, and an interconnecting hoist pipe circuit. The system is transported to the mining site by a ship with streamline and structural strengthening sections which are later detached and reassembled into an auxiliary vessel. The hoist pipe circuit is towed to the mining site in sections which, during assembly of the hoist pipe circuit, are used to lower the plant to the ocean bed. After being lowered, the plant covers the bottom, the Sessile ship following the course of the plant, continually hovering over it. A scraper bucket system mounted on arms incorporated by the plant scrape ore nodules from the surface of the bed. The plant cleans the nodules of valueless mud, crushes them to particle size and couples the ore particles to the hoist pipe circuit where they are lifted as slurry and deposited in bins of the hovering Sessile ship.

United States Patent [19] Dane, Jr.

[ DEEP SEA MINING SYSTEM [76] inventor: Ernest Blaney Dane, Jr., 57 Tyler Rd., Belmont, Mass. 02178 [22] Filed: Aug, 29, 1972 '21 App]. No.: 284,606

Related US. Application Data [63] Continuation-impart of Sei'. No. 148,853, June 1,

1971, abandoned, and a continuation-impart of Ser. N0.754,l9l,Aug.2l, l958.

52 us. c|.; 299/8, 37/58, 37/72, 2 37/DIG. 8 -511- Int. Cl E02f 7/00 [58] Field of Search 299/8, 9; 37/DlG; 8,58,

[56] References Cited UNITED STATES PATENTS 3,433,531 3/l969 Koot et a1. 299/8 3,522,670 8/1970 Flipse et al. 299/8 X 3,693,272 9/1972 Gariel 37/72 X 24,946 8/]859 Miller.... 37/109 Venus 37/58 X [451- May 21, 1974 Primary Examiner-Ernest R. Purser [57 ABSTRACT A deep sea mining system for mining ore from the surface of an ocean bed using a mining plant that travels the bed, a Sessile ship, and an interconnecting hoist pipe circuit. The system is transported to the mining site by a ship with streamline and structural strengthening sections which are later detached and reassembled into an auxiliary vessel. The hoist pipe circuit is towed to the mining site in sections which, during as sembly of the hoist pipe circuit, are used to lower the plant to the ocean bed. After being lowered, the plant covers the bottom, the Sessile ship following the course of the plant, continually hovering over it. A scraper bucket system mounted on arms incorporated by thevplant scrape ore nodules from the surface of the bed. The plant cleans the nodules of valueless mud, crushes them to particle size and couples the ore particles to the hoist pipe circuit where they are lifted as slurry and deposited in bins of the hovering Sessile ship.

20 Claims, 27 Drawing Figures SESSILE SHIP i'fiTENTEU um I 197 SHEET "02 0F 17 ORE BIN HATCH INVENTOR.

ERNEST B. DANE, BY I z%. L

SESSILE SHIP ATTORNEY PATENTEBMAYZHHYG saaupm 0F 17 AT ORNE'Y EMERGENCY DUMP VALVE INVENTOR. ERNEST B. DANE, JR.

iATENTEDWe saw user ADJOINING END OF'PIPE SECTIONS INVENTOR.

ERNEST B, DANE, JR.

LL 04AM),

ATTORNEY YZUHM 3811.730

sum as ur 17 fzsz MANBOT MAKING PIPE JUNCTION INVENTOR.

ATTORNEY SECOND PIPE SECTION HAUL DOWN OF PIPE 'ifig SECTIONS METERS MANBOT 262 OCEAN M BOTTOM 34F APPROX- FIRSTPIPE 34' 5,000 SECTION H METERS INVENTOR. ERNEST B. DANE, JR.

k 010mg,

AT RNEY PAIIzIIIzIIII zI I914 $81 1,730

' sum new 17 290 In I 5* LAST PIPE SECTION I I TERMINATION OF LAST PIPE SECTION INVENTOR.

ERNEST B. DANE, JR. BY

TTORNEY iATENTEfll-mfz rlsn I v 3 11 saw :10 0F 17 FIG. /0

DOUBLE JOINT AT MID LENGTH OF ARM SHOWN-IN FOLDED POSITION ASWHILE LOWERING lNl/ENTOR FAR END TERMINAL OF ARM A ERNEST DANE,

' ATTORNEY i 'maiminmm 221 i974 381L730 sum .n ur 17 356 III I sso TRACK v AXIS "0" 340 BUCKHET" AXIS b.

v 3I3u v I I 30' 30 Q 309 I X 9 v MINER WITH EXTENDED ARMS 358' r ,E 380 r 1 35s I f I INVENTOR. 359 ERNEST B. DANE, JR.

fiamu ATTORNEY ',rur; \ngnrm 21 I974 3:81 1,730

sum '12 0517 SIDE VIEW 3510 OF BUCKETS El DOWNSTREAM RUNNER/ v 352 CUTTING BLOCK I v I 2.50

BUCKET 3 SWATH MINED l-BY PRECEEDING BUCKET F /6. I214 FRONT vusw or BUCKETS INVENTOA ERNEST B. DANE, JR.

ATTORNEY m'liifl in HAY-21 m:

' saw in UP 17 Q XJQOOOQ mum - INVENTOA ERNEST B. DANE, JR 8 k%. Maw? ATTORNEY PATENTEUI'IAY 21 B74 sum -1snr'11 ORE CLEANER //vv/vr0k ERNEST B. DANE, JR.

ATTORNEY EATENTED AY I 9 3.811.730

sum 16 or 17.

PowER LINE FE 467. SPRING e 21' l DRIVE [Ll MoToR 455 46| [II I I 459 0 i GovERNoR REVERQBLE 1 LIMIT I CONTROL SWITCH GEAR MOTOR 55? BOX I L 46o' SPEED CONTROL SHAFT 452 F/G. l7

LIGHT HEAVY TENsIoN TENSION To COLLAR 36|c coLLAR 56m MEMBER I swIvEL 572 U IgfgME STEERING CONTROL 55:5] E63 F/ 6. /8

INNER OUTER 1?? I TRACK I [7 449 GEAR 447 1 45| I 322 I g DRIVE] 452 4 DRIVE MoToR 459 v INVENTOR. ERNEST B. DANE, JR.

ATTORNEY RA'YENTEU MAY 2 1 1974 sum 17 0F17 7 TO DRIVE /9 GEAR'NG SHEAVE 344 SIV I CRAWLER P ANT E I L R DR'VE TRANSFER WEIGHT MOTOR FUNCTION REFERENCE -3o2 SIGNAL WEIGHT CLEANED ORE RECOVERY TRANSDUCER IN SURGE RATE FOR 383 gag DEPOSIT FUNCTIONAL BLOCK DIAGRAM MoToR DRIVE 20 lNVENfOA ERNEST B. DANE, JR.

. V ATTORNEY DEEP SEA MINING SYSTEM This application is a continuation-in-part of my copending U.S. Pat. application Serial No. 148,853 which is now abandoned and is a continuation-in-part of U.S. Pat. application Ser. No. 754,191 filed Aug. 21, 1958 and subject to a' requirement for restriction.

This invention relates generally to ocean mining systems and particularly to systems for retrieving loose ore sediment from deep 'sea'floors.

INTRODUCTION The mineral resources of deep ocean beds though long recognized have yet to be fully exploited. Sufficient quantitiesof minerals lie loosely in the sediment of deep sea oozes to make their recovery in scale attractive. Of particular interest are-manganese nodules that are found in ocean sediments fonned under oxidizing conditions, and are especially widespread in the southeast Pacific Ocean. They are shaped like potatoes, mammilated cannon balls, marbles and also assume less identifiable forms. They range in size with diameters of between 0.5 to 25 cm, however, the majority of nodules recovered from deep sea dredging probes have not exceeded cm in diameter. Numerous photographs taken of the ocean floor indicate that they average about 3 cm' in diameter (See The Mineral Resources of the Sea, by-John L. Mero, Elsevier Publishing Company (1964)).

In addition to. manganese, the nodules contain a number of other minerals in adequate quantities, for example, ir'on, silicon, aluminum, copper and nickel, to

make them an attractive source of these as well. Mineral content is regional with comparatively high concentrations of iron in nodules near the western coasts of North and South America and the eastern coast of Asia, while nodules distant from Pacific islands and continental bodies possess relatively high nickel and copper content.

Most deposits are covered by between 2,000 and 6,000 meters of ocean. They are within the range of some deep submersible vehicles and sampling probes but the feasibility of mining them depends on the capability of recovery in scale, at the rate of many tons per day. I

PRIOR ART 3 Most ocean-mining systems of the prior art are directed toward recovery at comparatively shallow depths and at small scale. Drag dr'edges, for instance,

Moreover, systems such as these and others that are stationary may recover insufficient quantities of ore to make them economically unfeasible. In particular U.S. Pat.No. 3,522,670 granted Aug. 4, 197.0 to J. E. Flipse et a1. discloses apparatus for harvesting nodules with a gatheringmeans which is arranged to crawl around the bottom under control of TV. cameras and the like, but the gathering of nodules at any instant must be from the immediate locality of the expensive and complex gathering means. U.S. Pat. No. 3,433,531 to Koot recognizes the need to harvest from a substantial area around the lifting apparatus, and the desirability of crushing and treating the gathered material befor lifting it, but does not provide these features with the means hereindisclosed to move the plant rapidly, systematically, and in operating condition from place to place over the ocean floor, so that economic tonnages can be handled in regions where the nodules are of only moderate concentration.

SUMMARY OF INVENTION In view of the cited limitations in the art of ocean mining, applicant has as the primary object of his invention to provide a system for gathering loosely embedded minerals form deep ocean beds in' quantity.

It is another object of his invention to provide an efficient system for mining minerals from deep ocean floors.

It is a further object of his invention to provide a system for mining at ocean depths of 100 fathoms or more.

These and other objects are met by a system comprising a tractored central mining plant and a Sessile ship interconnected by a string of buoyant hoist-pipe sections. Except for the pipe sections which are carried I in tow, the system is transported to the mining site in the Sessile ship. To reduce drag and provide structural strengthening, the ship is equipped with streamlining, strengthening and propulsion sections that are detatchable at sea and may be reassembled into an auxiliary vessel. Upon reaching the mining site, the sections are separated and the Sessile ship is-erected. The mining plant is lowered by linking it up with the first and succeeding pipe sections one at a time. The hoist pipe circuit so formed is completed when the miner reaches the bottom and rests on the ocean floor..

The miner incorporates a tractored vehicle with a pair of arms projecting from its sides. Each arm carries a series of scraper buckets that ride on an endless chain that circulates along the length of the arm. As the vehicle travels the bottom linked with the hovering Sessile ship by the hoist pipe circuit, the circulating buckets scrape nodules on either side of the vehicle cutting a wide swath in the deposit. Gathered nodules are cleaned of valueless mud and crushed into particle size by apparatus on the vehicle. They enter the hoist pipe circuit as slurry and are pumped to temporary storage I cient as the ore is cleaned of mud prior to transport thereby reducing power consumption. Operation is continuous and involves no turn-around time except for initial deployment and final recovery of the miner which may be some weeks apart. The system is selfcontained, all necessary power, equipment, and facilities being supplied by the Sessile ship. These and other features'of the system will become apparent from the following detailed description; but this description should not be taken as a representation that the whole system or any parts of it have been actually constructed or actually observed and tested by me to operate in the manner described. This specification is to be read in application Serial 148,853 about to be abandoned which are to be transferred and made a part of this application to the extent that they may be of which:

DRAWINGS FIG. 1 is a sistant birds eye view of the system in transport to the mining site.

FIG. 2 is a side cut-away view of the freed Sessile ship of FIG. 1 in a vertical orientation.

FIG. 2A illustrates the bottom dump hatches of the ore bins in the ship.

FIG. 3 is a partial cross-sectional side view of two joined pipe sections of FIG. 1 illustrating the principal features of a typical pipe.

FIGS. 3A, 3B, and 3C are top cross-sectional views of the pipe of FIG. 3 along cutting planes AA, BB, and C-C, respectively, while FIG. 3D is a crosssectional view of the spherical tanks used in the lower pipe sections.

FIGS. 4 and 4A are side and vertical views, respectively, of the dump valve in the pipe section of FIG. 3.

FIG. 5 is a detailed side view of the secured junction of FIG. 3.

FIG. 6 is a side view of the Manbot used to construct the hoist pipe circuit and its operation in securing the pipe junction of FIGS. 3 and 5.

FIG. 7 illustrates the haul-down of pipe sections of FIG. 1 in the construction of the hoist pipe circuit.

FIG. 8 illustrates the terminal junction between the hoist pipe circuit and the Sessile ship of FIG. 3.

FIG. 9 is a front view of the folded arms of the miner of FIG. 8.

FIG. 10 is a side view of the double-joint fold of the arms of FIG. 9.

FIG. 11 is a distant vertical view of the miner of FIG. 2 with arms extended.

FIGS. 12 and 12A are side and front views, respectively, of the ore-gathering buckets mounted on the miners arms.

FIGS. 13 and 14 are side views of the near and far ends, respectively, of the miners arms.

FIG. 15 is a side view of the tractored vehicle of the miner.

FIG. 16 is a cut-away view of the ore cleaner in the vehicle of FIG. 15.

FIG. 17 is a diagram of a speed-control system for the tail-sheave tractor of .FIG. 14.

FIG. 18 illustrates a steering control system for the tail sheave tractor of FIG. 14.

FIG. 19 is a functional block diagram of a system for controlling the advance rate of the tractored vehicle of FIG. 15.

FIG. 20 illustrates a geared-motor drive for use in deep sea apparatus.

PREFERRED EMBODIMENT The surface components of the mining system are provided by a tender thatperforrns a mumber of functions to sustain the venture, including the following;

a. transports the miner to a distant mining site,

b. supplies power to the miner and hoist pipe circuit,

0. provides a control facility for all apparatus in the system,

d. stores ore mined from the ocean bed temporarily pending transfer to another ship,

lowering the miner and construction of the lengthly hoist pipe circuit therewith, for retrieving them upon conclusion of operations, and for receiving ore as it hovers over the miner working the ocean floor.

While conventional ships are adequate in some of the above respects, they may be troublesome with regard to the provision of a stable base in rough seas. During construction, the miner is lowered from the ship attached to the hoist pipe circuit as the latter is assembled from the floating pipe sections. The accumulating load may develop a mass of over 1,000 tons before the miner reaches the bottom. A large component of the static load is compensated by buoyancy tanks built into the respective pipe sections. However, the dynamic load produced by the massive ship as it rolls, pitches and heaves in the waves, some of which are in the order of 20 feet or more in height, is imposed fully on the construction hoists and the uppermost sections of the pipe circuit. Such dynamic loads could damage the pipe circuit or cause it to break away from the ship altogether.

The sensitivity of the hoist circuit to unwanted motion characteristic of conventional ships may be reduced by using complex compensating equipment in the pipe circuit. Alternatively, the surface terminal may be supplied by a semi-submerged catamaran, like those used on oil-drilling sea rigs. However, the preferred embodiment of the present system features a simpler and less expensive approach by incorporating a surface ship whose ratio of displacement change to total displacement as a function of depth from an assigned water-line is small compared to that of a conventional ship. Such features are realized in a Sessile" or Flip type ship illustrated in later FIG. 2 which has a relatively thin stem section and an assigned water-line midway up the stem. The section comprises a relatively narrow cylindrical steel shell bounded by two widening conical shells, with a slope of about 45. The upper conical shell merges into a cylindrically shaped double decked top while the lower conical shell is bounded by 4 a long and wide cylindrical shell that is submerged when the ship is erected along the vertical. The crosssectional area of the bottom cylinder is much greater than that of the stem section which is at the ocean surface. Consequently, changes in displacement due to wave action is significantly less than that of a conventional ship. Moreover, the massive ships submerged bottom provides substantial damping to motion, particularly heave, caused by waves.

The Sessile ship has a draft of about meters, which makes her too deep to float'jn many harbors. Therefore, she is conveyed from port to deeper water ina horizontal orientation. Because of the flatness of her top deck, she develops considerable drag or resistance to passage in the sea. Her velocity is accordingly limited to a few knots in this orientation. With the aid of special power drives adapted to propel the ship at inclined attitudes, say with her top deck a few feet or so above the surface, the ship with miner attached may be transported to a mining site at restricted speeds. As surface conditions change from calm to tough, the inclination of the ship may be varied by internal ballasting so 

1. In a deep sea mining plant for collecting and processing ore nodules on the ocean floor for delivery to a pipe circuit for hoisting to the ocean surface, the combination of; a vehicle adapted to travel said floor with a velocity Sv and including receiving means for receiving collected nodules, an ore cleaner for removing unwanted mud from said nodules, and means for transferring said cleaned nodules to said pipe, ore gathering apparatus mounted on said vehicle and extending over a substantial distance laterally from said vehicle to span a strip and adapted to collect nodules from said ocean floor along said distance and deliver them to said receiving means of said vehicle, said ore gathering apparatus having propulsion means adapted to travel said floor laterally spaced apart from said vehicle to move said apparatus with said vehicle while so extended, thereby to clear said nodules from said strip.
 2. The mining plant of claim 1 wherein said means for transporting said cleaned nodules to said pipe circuit includes a surge bin for accumulating said cleaned nodules from said cleaner, and said plant further includes first control means operatively associated with said bin adapted to vary the speed Sv of said vehicle so as to maintain the flow of said cleaned nodules into said bin essentially equal to the flow of said nodules to said pipe circuit.
 3. The mining plant of claim 2 wherein said first control means comprises a crawler drive motor for driving said vehicle, a weight transducer for measuring the weight of nodules in said bin and generating signals according to said weight, means for producing a weight reference signal according to a specified weight of nodules to be accumulated in said bin, and means for comparing said signals of said weight transducer with said weight reference signal and causing said crawler drive motor to adjust said speed Sv to maintain said weight of said nodules in said bin essentially at a specified level.
 4. A mining plant as set forth in claim 2 wherein said first control means is adapted to drive said vehicle at a speed SV corresponding with maintaining a substantially constant quantity of nodules in said bin.
 5. A mining plant ss set forth in claim 4 wherein said speed Sv corresponds with keeping said bin approximately half-filled with nodules.
 6. The mining plant of claim 4 wherein said ore gathering apparatus includes a track with an axis ''''c,'''' a series of scraper buckets circulating along the length of said track at a speed Sc with inbound buckets of said vehicle contributing to the support of said track and having open bottoms and an input axis ''''b'''' which is skewed forward of said axis ''''c'''' in the direction of said vehicle''s motion by an angle phi , and wherein said plant further includes inclined plate means extending from said receiving means to said ocean floor for providing a riding surface for said inbound buckets from said floor to the top of said receiving means whereby said nodules collected by said inbound buckets are slideably supported by said plate means until dumped into said receiving means.
 7. The mining plant of claim 6 wherein said track is extended at an angle theta relative to the negative of said velocity vector Sv, and wherein phi is substantially according to the relation. phi theta - tan 1 Sc sin theta /Sv + Sc cos theta .
 8. The mining plant of claim 4 wherein said ore gathering apparatus comprises a long arm projecting from said vehicle along an axis ''''c'''' describing an angle theta of substantially 90* relative to the negative of said velocity vector, with the distal end of said arm carried by a tail-sheave tractor, and an endless scraper which scrapes nodules inwardly from said distal end to said vehicle along said arm.
 9. A mining plant as set forth in claim 8 wherein said ore clEaner comprises a hollow inclined cylinder with an elevated end receiving said nodules from said receiving means, means for rotating said cylinder, a helical plate affixed to the internal surface of said cylinder along which said nodules may slide down said incline upon rotation of said cylinder, and means for directing jets of water on said sliding nodules to clean them.
 10. The combination as defined by claim 2 wherein said apparatus comprises a pair of long arms projecting from said vehicle at an angle theta of substantially 90* relative to the negative of said velocity vector Sv with the distal end of each arm carried by a tail-sheave tractor, and and endless scraper which scrapes nodules inwardly from said distal ends to said vehicle along said arms, wherein said vehicle comprises an ore crusher for reducing said cleaned nodules to particle size, and means for mixing said particle-sized nodules with fluid to produce ore slurry, in further combination with a Sessile ship adapted to hover over said plant, and a hoist pipe circuit adapted to pump ore slurry along its length, one end of said circuit connected to said ship and a second end connected to said plant and receiving said ore slurry porduced by said plant, said hoist pipe circuit comprising a series of hoist pipe sections each having a plurality of buoyancy tanks to provide a buoyant force amounting to at least half the weight of said pipe section loaded with ore, and a pump adapted to pump said ore slurry upward the length of said section.
 11. The combination as set forth in claim 10 wherein said first control means comprises a crawler drive motor for driving said vehicle, a weight transducer for measuring the weight of said bin and generating signals according to said weight means for producing a speed setting signal Sv'' according to a specified weight of said bin, and means for comparing said signals of said weight transducer with said speed setting signal and cooperating with said crawler drive motor to adjust said speed Sv to maintain the weight of said bin essentially as specified.
 12. The combination of claim 2 wherein said vehicle comprises an ore crusher and means for mixing the resulting crushed ore with water to form an ore slurry, in combination with a hoist pipe circuit comprising a plurality of interconnected sections, each section comprising pumping means, electrical connections, and a dump valve to clear the section in case of pumping failure.
 13. The combination of claim 12 having a hovering stable surface ship with ore bins for receiving said ore slurry and further including: a submerged float joined to said hoist pipe circuit providing it with a subsurface floating support, and a flexible, supported pipe connected between said ore bins of said ship and said hoist pipe circuit at said float for providing a flexible conduit for the flow of said slurry from said pipe circuit to said ore bins.
 14. The combination of claim 13 wherein said ore bins are located at about the same depth as said submerged float so that said flexible pipe is disposed substantially horizontally.
 15. The combination of claim 14 wherein said hoist pipe circuit is fabricated of buoyant material for reducing the load of said hoist circuit.
 16. The combination of claim 15 wherein said stable ship is a Sessile ship in a vertical orientation incorporating a stem section with a narrow stem and an assigned water-line crossing said narrow stem, and said ore bins are located in the bottom of said Sessile ship.
 17. A sea-going rig for harvesting manganese nodules and the like from the floor of the ocean, comprising, a. a plurality of long, buoyant hoist pipe sections, each comprising, pumping means to raise an ore slurry at a designed efficient rate, electrical connections for carrying electrical power to and through said sections, interconnecting means to permit said sections to be vertically assembled into a long conduit, an emErgency dump valve, and means for rafting said sections together for towing on the high seas, b. a miner comprising (ii) a vehicle adapted to move across the floor of the ocean with a velocity Sv and including receiving means for receiving collected nodules, an ore cleaner for removing unwanted mud from said nodules, and means for mixing said cleaned nodules with sea water for introduction into said conduit as a slurry, and (ii) ore gathering apparatus mounted on said vehicle and extending over a substantial distance laterally from said vehicle to span a strip and adapted to collect nodules from said ocean floor along said distance and deliver them to said receiving means, comprising propulsion means adapted to move said apparatus with said vehicle while so extended thereby to clean said nodules from said strip, c. a first control means for controlling the amount of water in said slurry responsive to the lowermost of said pumping means in operation, d. second control means for operating said dump valves, e. third control means for controlling said velocity to maintain a steady adequate supply of ore from said apparatus to said means for mixing, and f. a tender adapted to transport said miner from port to its operations area, to carry the equipment required to assemble said miner to the lowermost of said sections while in said operating area, and to lower said miner so attached to the ocean floor, and adapted to hover over said miner as it is in operation gathering and conveying said ore and to provide the electrical power for it its operation.
 18. The rig as defined by claim 17 wherein said tender is a flip ship adapted to navigate in a horizontal orientation, and to hover in a vertical orientation over said miner in operation.
 19. In the art of recovering ores comprising manganese nodules and the like from the ocean floor wherein the ore is elevated from the bottom of the ocean in a slurry carried by pumps through a very long conduit, said pumps and conduit being designed to deliver ore to the surface at a sufficiently high rate to be commercially economical, the method of harvesting comprising the steps of: a. carrying the lower end of said conduit along the floor of the ocean along a predetermined initial path at a controlled velocity, while gathering to said lower end nodules laterally across a wide strip bounded by a first edge and a second edge, b. gathering ore deposits on the ocean''s floor to said lower end from a substantial distance laterally and transverse to said path thereby clearing a strip having a first edge and a second edge, at least one of said edges being distinctively marked by said gathering step, c. cleaning the gathered ore by water jets at said lower end, d. mixing said ore with water in an amount controlled to achieve constant maximum efficiency of said conduit and pumps in raising said ore to the surface, and e. controlling the magnitude of said velocity so that the amount of ore gathered at said lower end is sufficient to supply ore for mixing in the required quantity to achieve constant maximum efficiency of said conduit and pumps in raising said ore to the surface, f. monitoring the ground at an edge of said strip at said distance to detect an edge previously distinctively marked, and g. controlling the direction of said velocity responsive to the detection of a previously marked edge to prevent overlapping of said strip.
 20. The method of claim 19 with the further step of crushing said ore prior to mixing. 